Method for improving the fatigue resistance of keratin fibers

Abstract

The invention relates to a method for improving the fatigue resistance of keratin fibers, comprising applying a cosmetical composition to the keratin fibers, wherein the composition comprises epsilon-polylysine, and wherein the method improves the resistance of the keratin fibers against repeated tensile stress.

Description

[0001] 2024P00008WQ 1 2025-11-05

[0002] Method for improving the fatigue resistance of keratin fibers

[0003] Technical Field

[0004] The present invention relates to a method for improving the fatigue resistance of keratin fibers by applying a cosmetic composition to the keratin fibers.

[0005] Background Art

[0006] Fatigue resistance of keratin fibers is a measure of the mechanical resistance of hair towards cyclic or repeated tensile stress. Hair is subjected to tensile stress by grooming and combing almost daily. During combing and grooming, hair is subject to repetitive stretching, which fatigues the hair and might finally lead to hair breakage.

[0007] Fatigue resistance of keratin fibers is particularly reduced in hair that has been treated by bleaching procedures and oxidative dyes. Thus, breakage occurs more often and earlier in bleached hair than in untreated hair.

[0008] This phenomenon is made visible to consumers by the amount of hair that gets stuck in their brushes or combs. Consumers therefore are looking for cosmetic products which prolong the lifetime of their hair and reduce early breakage of hair.

[0009] Fatigue resistance can be measured in terms of the average lifetime of keratin fibers subjected to repeated tensile stress in the longitudinal direction. The average lifetime describes the number of cycles of applied stress after which a certain percentage of fibers in a population of keratin fibers has fractured. An additional parameter for measuring fatigue resistance is the time of the onset of breakage. This parameter describes the number of cycles of applied stress after which the first keratin fibers in a population of keratin fibers begin to break.

[0010] From a consumer perspective, it is equally important to delay the onset of breakage as it is to increase the average lifetime of keratin fibers, because delaying the onset of breakage gives the consumer more time to apply hair-strengthening cosmetic 2024P00008WQ 2 2025-11-05 compositions and gives the treated hair more time to regenerate after, for example, an oxidative treatment.

[0011] Technical Problem

[0012] The present invention aims at providing cosmetic compositions and methods of using cosmetic compositions to improve the fatigue resistance of keratin fibers, particularly the fatigue resistance of keratin fibers in terms of their resistance towards tensile stress, particularly towards cyclic or repeated tensile stress. In particular, the invention aims at providing ways of preventing an early onset of breakage of keratin fibers. Thereby, the invention not only aims at improving the average lifetime of keratin fibers that are subjected to tensile stress, but also to delay the onset of earliest breakage of keratin fibers under repeated tensile stress.

[0013] Summary of the Invention

[0014] It has surprisingly been found that a cosmetic composition comprising epsilon- polylysine improves the fatigue resistance of keratin fibers in terms of their resistance to tensile stress. Even more surprisingly, it has been found that such a composition not only increases the average lifetime of keratin fibers under repeated tensile stress but also delays the onset of earliest breakage.

[0015] In a first aspect, the present invention therefore provides a method for improving the fatigue resistance of keratin fibers, comprising applying a cosmetical composition to the keratin fibers, wherein the composition comprises epsilon-polylysine, and wherein the method improves the resistance of the keratin fibers against repeated tensile stress.

[0016] Preferably, the keratin fibers are bleached keratin fibers.

[0017] Preferably, the method delays the onset of breakage of the keratin fibers under repeated tensile stress. Preferably, the method improves the fatigue resistance of keratin fibers at a relative humidity of more than 40 % RH.

[0018] Preferably, the composition comprises 0.001 % by weight to 10 % by weight of epsilon-polylysine, based on the total weight of the composition.

[0019] Preferably, the epsilon-polylysine is a polymer comprising 20 to 35 lysine units.

[0020] Preferably, the composition comprises 30 % by weight or more water, based on the total weight of the composition.

[0021] Preferably, the composition comprises one or more surfactants in an amount of 0.01 % by weight to 20 % by weight, based on the total weight of the composition.

[0022] Preferably, the composition is a shampoo, a conditioner, a hair oil or a hair mask.

[0023] Advantageous Effects of the Invention

[0024] The present invention provides a method for strengthening keratin fibers, particularly hair. Thereby, the invention allows to mitigate the damage caused by hair treatments such as bleaching or dying, as well as damage caused by other factors, such as mechanical stress or UV radiation. The use of a composition comprising epsilon- polylysine prevents or delays breakage of hair under cyclic or repeated tensile stress. In particular, hair treated according to the invention shows an increased lifetime and a delayed onset of breakage under repeated tensile stress.

[0025] Description of Embodiments

[0026] Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

[0027] Composition 2024P00008WQ 4 2025-11-05

[0028] The composition used according to the invention may preferably be a cosmetic composition for the treatment of hair. For example, the composition may be a shampoo, a conditioner, a hair oil, a hair mask, a hair spray, a styling gel or a styling wax. Preferably, the composition is a shampoo, a conditioner, a hair oil or a hair mask.

[0029] The composition may be fluid or solid. For example, the composition may have the form of a solution, a multiphase solution, a dispersion, a water-in-oil or oil-in-water emulsion, a PIT emulsion, a cream, a gel, a powder or a solid block. Preferably, the composition is fluid, more preferably, the composition is a solution, a multiphase solution, a dispersion, a water-in-oil or oil-in-water emulsion, a PIT emulsion, a cream, or a gel.

[0030] Epsilon-Polylysine

[0031] A first essential feature of the invention is the use of a composition containing epsilon-polylysine. Polylysine is a homopolymer of the amino acid lysine. Epsilon- polylysine consists of lysine monomer units linked predominantly or exclusively through their epsilon-amino group. Epsilon-polylysine can be synthesized or obtained from natural sources. Preferably, the epsilon-polylysine used in the invention is obtained from natural sources, for example by fermentation of bacteria, in particular bacteria of the genus Streptomyces. In one embodiment, the epsilon-polylysine is obtained from the species Streptomyces albulus. Naturally occurring epsilon- polylysine consists of L-lysine.

[0032] Preferably, epsilon-polylysine contains 2 to 50 lysine units, more preferably 10 to 40 lysine units, most preferably 20 to 35 lysine units.

[0033] The epsilon-polylysine may be branched or linear. Branched polylysine is preferably obtained synthetically. In a preferred embodiment, the epsilon-polylysine used in the invention is linear.

[0034] The composition comprises preferably 0.001 % by weight to 10 % by weight of epsilon-polylysine, more preferably 0.01 % by weight to 2.0 % by weight, most 2024P00008WQ 5 2025-11-05 preferably 0.05 % by weight to 1 .0 % by weight, based on the total weight of the composition.

[0035] Additional Components

[0036] Apart from epsilon-polylysine, the composition may comprise further components, such as surfactants, oils, solvents, cationic polymers, protein hydrolysates, fragrances, colorants, UV filters, vitamins, preservatives and antioxidants.

[0037] The composition may preferably comprise at least one surfactant. The use of a surfactant provides an additional cleaning effect to the composition and may help to solubilize the epsilon-polylysine and the optional other components. The surfactant may, for example, be selected from the group of anionic surfactants, nonionic surfactants, cationic surfactants and amphoteric surfactants. Preferably, the composition comprises at least one cationic surfactant.

[0038] The composition preferably comprises surfactants in a total amount of 0.01 % by weight to 20 % by weight, more preferably 0.1 % by weight to 15 % by weight, most preferably 1 % by weight to 10 % by weight, based on the total weight of the composition.

[0039] Cationic surfactants carry a positive charge in their hydrophilic part. This positive charge causes the surfactant molecules to attach to the negatively charged skin and hair surface. Thereby, cationic surfactants have a smoothing effect, increase hair shine, and contribute to moisture retention. Cationic surfactants also have a copreserving effect in cosmetic products due to their bactericidal effect.

[0040] Cationic surfactants may preferably be selected from the group of quaternary ammonium compounds, preferably cetrimonium chloride, behentrimonium chloride, and stearalkonium chloride; amine salts, preferably stearamidopropyl dimethylamine and isostearamidopropyl morpholine lactate; imidazolinium derivatives, preferably dihydroxyethyl stearamidoimidazoline; quaternary imidazolines, preferably the imidazolium compounds known under the INCI designations quaternium-27, quaternium-83, quaternium-87 and quaternium-91 ; pyridinium compounds, preferably cetylpyridinium chloride; and phosphonium salts. Preferably, cationic surfactants are selected from the group of quaternary ammonium compounds, amine salts, and imidazolinium derivatives.

[0041] The composition preferably comprises cationic surfactants in a total amount of 0.01 % by weight to 20 % by weight, more preferably 0.1 % by weight to 12 % by weight, most preferably 0.5 % by weight to 10 % by weight, based on the total weight of the composition.

[0042] Anionic surfactants may, for example, be selected from surfactants having a sulfonate, sulfate or carboxylic acid group. The anionic surfactants are preferably selected from the group of alkyl sulfates, alkyl ether sulfates, alkylsulfosuccinates, olefin sulfonates, alkyl ether sulfosuccinates, acylisethionates, acylsarcosinates, alkyl ether carboxylates, polyoxyalkylenated alkylamido ether carboxylic acids, acylglutamates, and acylglycinates. The acyl and alkyl groups of these surfactants preferably comprise 6 to 30 carbon atoms, more preferably 12 to 28 carbon atoms, even more preferably 14 to 24 carbon atoms, most preferably 16 to 22 carbon atoms. The anionic surfactants may be used in acid form or as salts of alkali metals, alkaline-earth metals, ammonium, or amino alcohols.

[0043] Nonionic surfactants may preferably be selected from the group of alkoxylated alkylphenols, alkoxylated fatty alcohols, alkoxylated fatty acid amides, esters of acids and polyethylene glycols, ethoxylated glyceryl esters of fatty acids, alkoxylated esters of acids and sorbitol, esters of fatty acids and sucrose, alkyl(poly)glucosides, alkoxylated alkyl(poly)glucosides, alkenyl(poly)glucosides, alkoxylated alkenyl(poly)glucosides, alkoxylated plant oils, and amine oxides. Particularly preferred nonionic surfactants are alkoxylated fatty alcohols, alkyl(poly)glucosides and alkoxylated alkyl(poly)glucosides.

[0044] Amphoteric surfactants may preferably be selected from the group of alkylbetaines, such as cocoylbetaine, and alkylamido-alkylbetaines, such as cocoam idopropylbetaine. 2024P00008WQ 7 2025-11-05

[0045] The composition may further comprise one or more biosurfactants. The term biosurfactants refers to surfactants that can be obtained from microbial sources.

[0046] In a preferred embodiment, the composition comprises a biosurfactant selected from the group consisting of rhamnolipids, sophorolipids, mannosylerythritol lipids, surfactin, liamocins and fengycins. The composition may also contain mixtures of several of these biosurfactants.

[0047] The total amount of biosurfactants in the composition is preferably 1 % by weight to 20 % by weight, preferably 2 % by weight to 15 % by weight, most preferably 3 % by weight to 10 % by weight, based on the total weight of the composition.

[0048] The composition may preferably comprise one or more oils. Oils may preferably be selected from the group of silicones, such as dimethicone and amodimethicone; plant oils, such as argan oil and coconut oil; mineral oils, such as isoparaffins and synthetic hydrocarbons; saturated and unsaturated fatty alcohols, such as cetyl alcohol, stearyl alcohol, cetearyl alcohol, oleyl alcohol and octyldodecanol; dialkyl ethers, such as dicaprylyl ether; and esters, such as isopropyl myristate.

[0049] The composition preferably comprises oils in a total amount of 0.01 % by weight to 10 % by weight, more preferably 0.05 % by weight to 5 % by weight, most preferably 0.1 % by weight to 2 % by weight, based on the total weight of the composition. In another embodiment, the total amount of oils is 80 % by weight or more, preferably 90 % by weight or more. Such compositions can be used, for example, as hair oils.

[0050] The composition may further comprise one or more fatty alcohols, preferably fatty alcohols comprising 8 or more carbon atoms, more preferably 8 to 20 carbon atoms. Suitable fatty alcohols include capryl alcohol, 2-ethylhexyl alcohol, caprin alcohol, lauryl alcohol, isotridecyl alcohol, myristyl alcohol, cetyl alcohol, palmoleyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol, elaidyl alcohol, petroselinyl alcohol, linolyl alcohol, linolenyl alcohol, elaeostearyl alcohol, arachidyl alcohol, gadoleyl alcohol, behenyl alcohol, erucyl alcohol, and brassidyl alcohol. 2024P00008WQ 8 2025-11-05

[0051] The composition preferably includes fatty alcohols in a total amount of 0,1 % by weight to 20 % by weight, preferably 0,2 % by weight to 17 % by weight, more preferably 0.5 % by weight to 10 % by weight, based on the total weight of the composition.

[0052] The composition may preferably comprise at least one solvent selected from water and organic solvents. Suitable organic solvents are preferably selected from the group of mono- or polyalcohols with 1 to 6 carbon atoms. Preferred organic solvents are selected from ethanol, isopropanol, glycerol, and propylene glycol.

[0053] The composition preferably comprises water in a total amount of 30 % by weight or more, more preferably 60 % by weight or more, most preferably 80 % by weight or more, based on the total weight of the composition.

[0054] The composition preferably comprises organic solvents in a total amount of 0.1 % by weight to 10 % by weight, more preferably 0.2 % by weight to 5 % by weight, most preferably 0.5 % by weight to 2 % by weight, based on the total weight of the composition.

[0055] The composition may preferably comprise at least one cationic polymer. Preferably, the cationic polymer is a modified polysaccharide. Cationic polymers have conditioning properties in that they provide a pleasant feeling on the scalp. Cationic polymers may preferably be selected from the group of quaternized cellulose polymers, such as polyquaternium-10; hydrophobically modified cationic cellulose derivatives, such as polyquaternium-67; cationic inulin polymers, such as hydroxypropyltrimonium inulin; cationic cassia polymers, such as cassia hydroxypropyltrimonium chloride; cationic alkyl polyglycosides; cationized honey, such as Honeyquat® 50; cationic guar derivatives, such as hydroxypropyl guar hydroxypropyltrimonium chloride and / or guar hydroxypropyltrimonium chloride; polymeric dimethyldiallylammonium salts and their copolymers with esters and amides of acrylic acid and methacrylic acid, such as polyquaternium-6 and polyquaternium-7; copolymers of vinyl pyrrolidone with quaternized derivatives of dialkylaminoalkyl acrylate and methacrylate, such as vinyl pyrrolidone- dimethylaminoethyl methacrylate copolymers quaternized with diethyl sulfate; vinylpyrrolidone-vinylimidazolium methochloride copolymers; quaternized polyvinyl alcohol; and polymers such as polyquaternium-2, polyquaternium-16, polyquaternium-17, polyquaternium-18, polyquaternium-24, polyquaternium-27, polyquaternium-32, polyquaternium-37, polyquaternium-74, and polyquaternium-89. Preferably, the cationic polymer is a cationic guar derivative.

[0056] The composition preferably comprises cationic polymers in a total amount of 0.1 % by weight to 10 % by weight, more preferably 0.2 % by weight to 5 % by weight, most preferably 0.5 % by weight to 2 % by weight, based on the total weight of the composition.

[0057] The composition may also contain a protein hydrolysate. A protein hydrolysate is a complex mixture of peptides and amino acids obtained by hydrolyzing a protein composition. Preferably, the protein hydrolysate is obtained from plant sources, such as pea, potato, silk and wheat. In a preferred embodiment the protein hydrolysate is selected from the group of hydrolyzed keratins, pea proteins, potato proteins, silk proteins, and wheat proteins.

[0058] The composition preferably comprises protein hydrolysates in a total amount of 0.01 % by weight to 10 % by weight, more preferably 0.05 % by weight to 3 % by weight, most preferably 0.1 % by weight to 1 % by weight, based on the total weight of the composition.

[0059] The composition may further comprise foaming agents, such as fatty acid amides of alkanolamines, for example cocamide monoethanolamine.

[0060] The composition may further comprise other components selected from the group of perfumes, such as perfume oils and encapsulated perfumes; UV filters; colorants to color the composition; skin care agents, such as bisabolol and allantoin; complexing agents, such as EDTA, NTA, beta-alanine diacetic acid and phosphonic acids; sphingolipids, such as ceramides and pseudo-ceramides; antioxidants, such as betacarotin and tocopherylacetate; preservatives, such as sodium benzoate, salicylic acid, parabens, phenoxyethanol, and ethylhexylglycerol; pH-adjusting agents, such as sodium hydroxide, citric acid and lactic acid; viscosity regulators, such as sodium 2024P00008WG 10 2025-11 -05 chloride; and vitamins and pro-vitamins, such as vitamin E, niacinamide and panthenol.

[0061] The amount of these other components is preferably limited to 10 % by weight or less, based on the total weight of the composition.

[0062] The composition may also comprise one or more additional anti-dandruff agents, such as piroctone olamine. However, this is not strictly necessary, because epsilon- polylysine may itself have an anti-dandruff effect. Therefore, the composition preferably does not comprise any additional anti-dandruff agent.

[0063] The composition preferably has a pH of 2 to 6, more preferably 2.5 to 5.5, most preferably 3 to 5.

[0064] Exemplary compositions

[0065] An exemplary shampoo composition according to the invention comprises

[0066] 8 % by weight to 12 % by weight fatty alcohol ether sulfate (e.g. sodium laureth sulfate);

[0067] 3 % by weight to 5 % by weight amphoteric surfactant (e.g. cocoamidopropyl betaine);

[0068] 1 % by weight to 3 % by weight fatty alcohol sulfate (e.g. ammonium lauryl sulfate);

[0069] 0.01 % by weight to 0.2 % by weight epsilon-polylysine;

[0070] 0.5 % by weight to 1 % by weight foaming agent (e.g. cocamide monoethanolamine); 0.5 % by weight to 2 % by weight nonionic surfactant (e.g. PEG-7 glyceryl cocoate);

[0071] 0.1 % by weight to 0.5 % by weight hydrolyzed protein (e.g. hydrolyzed keratin); miscellaneous components, such as preservatives, vitamins, amino acids, and perfumes; and water.

[0072] Another exemplary shampoo composition according to the invention comprises

[0073] 6 % by weight to 8 % by weight fatty alcohol sulfate (e.g. ammonium lauryl sulfate);

[0074] 3 % by weight to 5 % by weight amphoteric surfactant (e.g. cocoamphodiacetate);

[0075] 3 % by weight to 4 % by weight alkyl glucoside (e.g. coco glucoside); 2024P00008WG 11 2025-11-05

[0076] 0.2 % by weight to 0.6 % by weight silicone oil (e.g. dimethicone);

[0077] 0.3 % by weight to 0.6 % by weight hydrogenated plant oil (e.g. hydrogenated castor oil);

[0078] 0.01 % by weight to 0.1 % by weight epsilon-polylysine;

[0079] 0.1 % by weight to 0.5 % by weight hydrolyzed protein (e.g. hydrolyzed wheat protein); miscellaneous components, such as preservatives, vitamins, amino acids, and perfumes; and water.

[0080] An exemplary conditioner composition according to the invention comprises 0.5 % by weight to 1 .0 % by weight cationic surfactants (e.g. quaternium-87); 0.5 % by weight to 1 .5 % by weight ester oil (e.g. glycol distearate);

[0081] 4 % by weight to 6 % by weight fatty alcohol (e.g. cetearyl alcohol);

[0082] 0.5 % by weight to 1 .5 % by weight hydroxypropylgluconamide and hydroxypropylammonium gluconate;

[0083] 0.2 % by weight to 4 % by weight cationic polymers (e.g. polyquaternium-37 and behenoyl PG-trimonium chloride, behentrimonium chloride);

[0084] 1 .0 % by weight to 2.0 % by weight wax (e.g. shea butter);

[0085] 0.3 % by weight to 1.0 % by weight epsilon-polylysine; miscellaneous components, such as preservatives, vitamins, amino acids, and perfumes; and water.

[0086] Method of Use

[0087] The composition is used for improving the fatigue resistance of keratin fibers. In the context of the invention, this means that the application of the composition onto keratin fibers improves the resistance of the keratin fibers against repeated tensile stress. Preferably, the composition is used on human hair.

[0088] Tensile stress refers to stress caused primarily by pulling forces applied in the longitudinal direction of the keratin fibers. Such stress occurs, for example, during combing or grooming of the keratin fibers. By improving the resistance against cyclic tensile stress, the use of the composition prevents or delays breakage of the hair fibers.

[0089] Preferably, the composition is used to delay the onset of earliest breakage of hair. The onset of earliest breakage may, for example, be determined by the method disclosed in the examples of this application.

[0090] In a preferred embodiment, the composition is used to improve the fatigue resistance of bleached keratin fibers. This refers to keratin fibers that have been subjected to one or more oxidative treatments, including keratin fibers subjected to UV radiation and to oxidative chemicals. Preferably, the composition is used on keratin fibers that have been subjected to oxidative chemicals, such as oxidative dyes.

[0091] In a preferred embodiment, the composition is used to improve the fatigue resistance of keratin fibers in an environment with a high relative humidity. It is known that hair breakage is promoted in humid environments, as humidity reduces the force required to break hair. Therefore, the composition is preferably used to improve the fatigue resistance of keratin fibers at a relative humidity of more than 40 % RH, more preferably more than 45 % RH, most preferably more than 50 % RH.

[0092] The composition is preferably applied to keratin fibers by hand. Preferably, the composition is distributed over the keratin fibers after its application. The composition may also be applied onto the skin, for example the scalp, of a subject. The composition may be applied to dry or wet keratin fibers. Preferably, the keratin fibers are wetted, preferably with water, before applying the composition. The composition can be left on the keratin fibers for an indefinite amount of time (leave-on composition) or can be washed off the keratin fibers shortly after its application.

[0093] Preferably, the composition is washed off the keratin fibers, preferably after 5 minutes or less after its application. Preferably, the composition is washed off with water.

[0094] Examples

[0095] Hereinafter, the present invention will be more specifically described based on examples, but the present invention is not limited to the following examples. 2024P00008WQ 13 2025-11-05

[0096] The following protocol was used to determine the effect of different cosmetic compositions on the fatigue resistance of hair.

[0097] Hair tresses were subjected to one or two bleaching treatments. Each bleaching treatment was carried out by treating the hair tresses with a combination of a commercially available lightening powder (Blond Me Enforcing Premium Lift 9+, Schwarzkopf) and a commercially available developer (9 % hydrogen peroxide) at a ratio of 1 :2 for 45 minutes, with a 2-minute wash between bleaching treatments. The bleached hair tresses were soaked in 200 ml of the respective cosmetic composition while stirring at 60 rpm for 60 minutes at a temperature of 55 °C. Then the tresses were gently washed under running tap water for about 2 minutes and air dried. Single hair fibers (N = 40) were randomly cut from the dried hair tresses and were subjected to repeated tensile stress using a commercially available fiber-testing instrument (Dia-stron CYC802). The instrument repeatedly applied a 5 % nominal constant strain at a rate of 40 mm / s until the fiber broke. For each fiber, the number cycles of applied tensile stress until breakage was recorded. All experiments were performed within a humidity chamber providing a predetermined relative humidity of 55 % + / - 2 % RH at a temperature of 22 °C + / - 2 °C.

[0098] The survival probability of individual hair fibers as a function of the number of cycles of applied tensile stress was analyzed using a Weibull distribution as described elsewhere (Evans TA. Fatigue testing of hair-a statistical approach to hair breakage. J Cosmet Sci. 2009 Nov-Dec; 60(6):599-616) to determine the average lifetime parameter a and the shape parameter [3 of the best-fitting Weibull distribution. The 95 % confidence interval (Cl) was determined using the least-squares method.

[0099] The following cosmetic compositions was tested using the above protocol: an aqueous solution of 0.62 % (w / v) linear epsilon-polylysine containing an average of 25 to 30 units of lysine (composition A). The composition was applied to hair tresses that had been subjected to two bleaching treatments (2x bleached). The results were compared to hair tresses subjected to two (2x bleached) or only a single bleaching treatment (1x bleached) and to hair that was neither bleached nor treated with any cosmetic composition. 2024P00008WC 14 2025-11-05

[0100] The results are shown in the following table.

[0101] Table 1

[0102] The use of a polylysine-containing composition according to the invention resulted in an increase of both the average lifetime as well as the shape parameter as compared to 2x and 1x bleached hair to levels comparable with that of unbleached hair. The increase in the shape parameter indicates a reduction in of early breakage because of polylysine. Thus, the use of a composition including epsilon-polylysine leads to a strengthening of hair as evidenced by the increased lifetime and to a reduction of early breakage of bleached hair. In summary, the data show that the use of a composition according to the invention strengthens hair and prevents hair breakage caused by repeated tensile stress.

Claims

2024P00008WQ 15 2025-11-05Claims1 . A method for improving the fatigue resistance of keratin fibers, comprising applying a cosmetical composition to the keratin fibers, wherein the composition comprises epsilon-polylysine, and wherein the method improves the resistance of the keratin fibers against repeated tensile stress.

2. The method according to claim 1 , wherein the keratin fibers are bleached keratin fibers.

3. The method according to claim 1 or 2, wherein the method delays the onset of breakage of the keratin fibers under repeated tensile stress.

4. The method according to any one of claims 1 to 3, where the method improves the fatigue resistance of keratin fibers at a relative humidity of more than 40 % RH.

5. The method according to any one of claims 1 to 4, wherein the composition comprises 0.001 % by weight to 10 % by weight of epsilon-polylysine, based on the total weight of the composition.

6. The method according to any one of claims 1 to 5, wherein the epsilon- polylysine is a polymer comprising 20 to 35 lysine units.

7. The method according to any one of claims 1 to 6, wherein the composition comprises 30 % by weight or more water, based on the total weight of the composition.

8. The method according to any one of claims 1 to 7, wherein the composition comprises one or more surfactants in an amount of 0.01 % by weight to 20 % by weight, based on the total weight of the composition.

9. The method according to any one of claims 1 to 8, wherein the composition is a shampoo, a conditioner, a hair oil or a hair mask.

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